This invention relates to a low trauma, reversible flow pumping system with an improved two-way, gravity actuated check valve means for transfer of biological fluids containing fragile components such as cell culture suspensions and blood or biohazardous materials which require high containment levels.
Pump transfer of biological fluids that contain fragile components or of fluids that are an environmental hazard present special problems. Most conventional pumping systems exert high shear and grinding action on fluid components and/or do not provide complete containment in the event of mechanical failure. Sterilization and maintenance of absolute sterility is also difficult with many pump types. Thus, the conventional impeller driven, gear and piston type pumps produce damage to fragile components and are difficult to sterilize. For such reasons, they are rarely used for transfer of mammalian cell culture suspensions or blood which contain fragile cellular elements.
Diaphragm, bellows and peristaltic type pumps produce less trauma, but present a major problem of leakage if a mechanical failure occurs. Mechanical failures can be expected to eventually occur in such systems due to the stretching and frictional wear of elastic components. Also, the diaphragm and bellows type pumps do not provide a confined flow path, and regions of these pumps can become filled with particulate matter if fluid containing suspended material is transferred such as cell culture suspensions.
Although peristaltic type pumps in which the pumped fluid does not contact any part of the pump mechanism are generally used for the transfer of biological fluids which contain fragile components, certain elastic tube or balloon type pumping systems have been developed heretofor to provide a more gentle pulsatile flow under sterile conditions. U.S. Pat. Nos. 3,406,633; 3,568,214; 3,639,084; and 3,883,272 illustrate such pumping systems in medical applications. In these devices, the alternate expansion and contraction of an elastic tube or balloon element under the influence of oscillatory pressure provides a gentle pulsatile flow of fluid through the elastic element. However, for medical applications the pumps are unidirectional and insofar as the expandable pump elements are elastic, they are subject to eventual rupture or other such mechanical failure.
In said copending application Ser. No. 291,216, a low trauma, reversible flow pumping system is disclosed which is useful for transfer of such biological fluids containing fragile components and for biohazardous materials which require high containment levels. The pumping system comprises a length of collapsible and flexible tubing having inlet and outlet means at opposite ends, each said end being in fluid communication with a two-way, gravity actuated check valve means to permit fluid to be pumped through said tubing in either direction, said tubing being sealingly enclosed within a hydraulic fluid containing chamber and said chamber being in fluid communication with oscillatory pressure providing means to provide alternate expansion and collapsing of said collapsible and flexible tubing. This pumping system produces minimal trauma to fragile components of the pumped liquid. The direction of flow in the pumped circuit can be readily reversed by inverting the pump head and its check valves. The reverse flow is particularly useful in cell culture systems in which it is desired to unclog lines which may have become plugged with cellular matter, to provide back-flow of microcarrier particles which are used in some cell culture systems and to avoid product loss during changeover of individual vessels in the cell culture system such as filter vessels and the like.
In each two-way, gravity actuated check valve of said copending application Ser. No. 291,216, provision is made for vertical movement of an elongated slidable weight member between upper and lower beveled seats within a cylindrical chamber. During operation of the pumping system, gravity holds the slidable weight member of the lower check valve in a sealing position against the lower beveled seat and thereby allows fluid in the pump head zone to be pressure pumped in an upward direction through the upper check valve and simultaneously prevents fluid flow in the downward direction. The direction of flow can be readily changed by inversion of the pump head and the two check valves.